Silver complex diffusion transfer process



United States Patent 3,360,368 SILVER COMPLEX DIFFUSION TRANSFER PROCESS George Frans Van Veelen and Eric Maria Brinckman, Mortsel-Antwerp, and Jozef Frans Willems and Gerard Michiel Sevens, Wilrijk-Antwerp, Belgium, assignors to Gevaert Photo-Producten N.V., Mortsel, Belgium, a company of Belgium No Drawing. Filed July 5, 1962, Ser. No. 207,816 Claims priority, application Belgium, July 6, 1961, 40,787 10 Claims. (CI. 96-29) The present invention relates to a photographic silver complex diffusion transfer process and to a material for use in such a process whereby diffusion transfer images are obtained with black or bluish-black image-tones.

According to the known silver complex diffusion transfer processes, the principle of which is descirbed in the US. patent specification 2,352,014 and in German patent specification 887,733, a light-sensitive silver halide emulsion layer is exposed to an image and then pressed into contact with a specially prepared receiving material in the presence of a developer and a silver halide complexing agent. The exposed image areas are developed and dornot undergo any further change. The undeveloped silver halide in the unexposed areas is complexed by the silver halide complexing agent which is present either in the developer or in the receiving layer, transferred by diffusion to the receiving layer of said image-receiving material and converted therein to metallic silver. The conversion is promoted by the action of reducing nuclei. In this way, a positive image of the original is formed in the receiving layer and is apparent after separation of the latter from the silver halide emulsion layer.

In addition to the classical development by means of an organic reducing agent in the presence of photochemical nuclei, finely divided metal such as colloidal silver or metal sulfides such as cobalt sulfide can initiate and catalyze the development in the receiving layer of the transferred silver complex to a metallic silver image. A disadvantage of the silver complex diifusion transfer process specially when using metal sulfide nuclei is the brownish image tone of the obtained silver image.

This disadvantage is overcome by adding a black-toning agent, generally an organic heterocycl'ic compound containing mercapto groups. Many of the hitherto known compounds show simultaneously with the desired improvement of the image tone the disadvantage of delaying the formation of the image in the image-receiving material. In this way a longer contact time is needed for obtaining sufiiciently strong copies. The used amounts of these compounds have to be kept between determined and rather narrow limits since too high a concentration of blacktoning agent even can completely prevent the development.

It has now been found to obtain black or bluish-black dilfusion transfer images without the above mentioned side-effects if in the silver complex diffusion transfer process tetrahydro-ZH-1,3-thiazine-2-thione or tetrahydro- 2H-1,3-oxazine-2-thione compounds are used corresponding to the following general formula, or tautomeric structures thereof:

IS NH wherein X represents a sulfur atom or an oxygen atom, and each of R R R R R and R (the same or different) Suited compounds of this type are e.g.:

tetrahydro-2H-1,3-thiazlne-3-thione 4,4,G-trimethyl tetrahydro-2H-1,3-thiazine-2-thione tetral1ydro-2H-1,3-oXazine-2-thione I S NH C 2 G-methyltetrabydroQHd,3-oxazine-2thione I S /NH C 4,4,6- trimethyltetrahydr0-2H-1,3-oxazine-2-tl1ione The preparation of compounds 1, 2 and 3 mainly consists of the condensation of the corresponding halogen amino compounds with carbon disulfide and of ring closure with hydrochloric acid.

The preparation of compound 1 is described in Chem. Ber. 23 (1890) 91.

The preparation of compound 2 is described in the French patent specification 1,094,167. The preparation of compound 3 is described in J. Am. Chem. Soc., 77 (1955), 2868.

Compound 4 is prepared as follows:

37.5 g. of 3-aminopropanol-1 are dissolved in cm. of water whereupon, while strongly stirring, 30 cm. of carbon disulfide and a solution of 28 g. of potassium hydroxide in 150 cm. of water are added. As soon as the carbon disulfide has completely dissolved another solution of 28 g. of potassium hydroxide in 150 cm. of water is added to the clear red solution. Then, while strongly stirring, a solution of 165 g. of lead nitrate in 600 cm. of water is dropwise added whereupon stirring is continued for 2 hrs. The precipitated lead sulfide is allowed to settle down for 24 hrs., then filtered off and three times washed with 150 cm. of water. The filtrate is evaporated on a water-bath and by means of a water-jet vacuum pump until crystallization starts (volume of about 300 cmfi). Further crystallization takes place at a temperature below freezing point.

The white crystals of tetrahydro-2H-1,3-oxazine-2- thione are sucked off and recrystallized from 175 cm. of isopropanol.

Yield: 30 g. Melting point: 130 C.

Compound 5 can be prepared as follows:

26.4 g. of 4-amino-butanol-2 and 16.8 g. of potassium hydroxide are dissolved in 60 cm. of water whereupon, while stirring 18 cm. of carbon disulfide are dropwise added. The mixture is warmed up till 40-45 C. and an orange-red solution is obtained. First a solution of 16.8 g. of potassium hydroxide in 360 cm. of water is added and then dropwise whilst strongly stirring a solution of 99 g. of lead nitrate in 540 cm. of water. Stirring is continued for 2 hrs. and then the solution is warmed up for a short while till 60 C. before the precipitate of lead sulfide is allowed to settle down for 24 hrs. Thereupon the bad sulfide is filtered off and three times washed with 100 cm. of water. The filtrate is evaporated on a waterbath and by means of a water-jet vacuum pump until crystallization starts (volume of about 200 cmfi). Further crystallization takes place at a temperature below freezing point. The crystals of 6-methyl-tetrahydro-2H- 1,3-oxazine-2-thione are sucked off and recrystallized from ethanol. Yield: 15 g. Melting point: 140 C.

Finally, the preparation of compound 6 is described in the US. patent specification 2,832,680.

The black-toning agents according to the invention may be present in the developing bath and/ or in the imagereceiving material and/or in the light-sensitive material.

When the black-toning agent is incorporated into the treating bath solution, it is preferably added in a concentration of between 20 mg. of about 250 mg. per litre.

When the black-toning agent is present in the lightsensitive material, preferably from 5 to 20 mg. of blacktoning agent are present per sq. m. In this case the blacktoning agent according to the invention can be present in any water-permeable layer, which is coated at the same side of the support as the light-sensitive silver halide emulsion layer and from which the black-toning agent can diffuse to the image-receiving layer of the imagereceiving material, e.g. in the light-sensitive silver halide emulsion lay-er itself, in a covering layer etc.

Finally, the black-toning agent can be present in the image-receiving matreial namely in the image-receiving layer and/or in a water-permeable layer which is in effective contact with the image-receiving layer so that the black-toning agent can diffuse in due time to the imagereceiving layer- In this case the black-toning agent is preferably added in an amount of about 10 to about 300 mg. per sq. m. of image-receiving material.

The image-receiving material, which can be used in this invention, mostly consists of a support, for instance of paper, onto which one or more layers are coated. One of said layers is an image-receiving layer or a nuclei containing layer, wherein the diffusion transfer image is formed in the presence of physical and/ or chemical developing nuclei or substances which are able to form such developing nuclei with the diffusing silver complex. The image-receiving material can also consist of a paper support alone wherein substances such as developing nuclei are incorporated.

A material which is suited for obtaining many positive copies of an original by means of one single imagewise exposed light-sensitive material, can also be used as an image-receiving material. This kind of image-receiv- 4 ing material is described egg. in the Belgian patent specifications 595,323 and 595,324.

The image-receiving layer can also be coated on the same support as the silver halide emulsion layer. In this case the image-receiving layer is mostly applied onto a support e.g. of paper and then coated with a slightly or not hardened light-sensitive silver halide emulsion layer. This kind of image-receiving material is described in the British patent specification 654,631. After exposure, development and diffusion transfer to the image-receiving layer, the exposed and developed unhardened emulsion layer can be removed e.g. by washing with warm water, or by stripping off after having been in contact with a sheet of common paper.

The light-sensitive material, which is suited for being applied in a diffusion transfer process wherein blacktoning agents may be used as described above, may be any light-sensitive silver halide material, of which the exposed silver halide is developed and the unexposed silver halide is complexed in a sufficiently rapid way to allow the forming of a diffusion transfer image. Silver chloride emulsions, which may also contain silver bromide or silver iodide or to which certain ingredients may be added for obtaining the desired emulsion characteristics, are preferably used.

The developing substance(s) can be incorporated into the light-sensitive material and/ or into the bath and/or into the image-receiving material. Suited developing substances are among others: hydroquinone, monomethyl-paminophenyl sulfate, aminophenol, 3-pyrazolidone compounds and mixtures of these developing substances such as the mixture of hydroquinone and a 3-pyrazolidone derivative which can be incorporated in the image-receiving material as described in the Belgian patent specification 6llj637.

The complexing agent which forms a soluble complex with the silver halide is preferably an alkali thiosulfate and can be incorporated either into the image-receiving material or into the processing bath.

Sulfides of heavy metals e.g. of antimony, bismuth, cadmium, cobalt, lead, nickel and silver, heavy metals preferably in colloidal form, such as silver, gold, platina, palladium and mercury, and/or other substances which can be used as developing nuclei for the complexed silver halide are incorporated in the image-receiving layer.

In many cases an antifogging compound is used to avoid fogging in the exposed silver halide emulsion layers. This antifogging compound can be worked up in the light-sensitive emulsion and/ or in the processing bath.

The substances such as developers, complexing agents for silver halide, alkali, development nuclei and others which are needed in the silver complex diffusion transfer process can all be worked up in the used light-sensitive or image-receiving material so that eventually common water can be used as processing liquid (Belgian patent specification 612,103).

For further details about the exposing and developing apparatus which can be used, the silver complex diffusion transfer process in general and the materials which are suited for this process, there can be referred by way of example to Progress in Photography" vol. I, 1940-1950, pp. 76-77 and vol. II, 1951-1954, pp. 156-167; vol. III, 1955-1958, pp. 24-36 and to the patent literature cited therein.

The following examples illustrate the present invention.

Example 1 The light-sensitive material is prepared as follows:

To 1 kg. of a gelatino silver chloride emulsion which is prepared from 45 g. of silver nitrate and which is sensitized to light with a wavelength of 500-570 m r a solution of 250 mg. of 6-methyl-tetrahydro-2H-1,3-thiazine- 2-thione in 25 cm. of ethanol is added. This emulsion is coated onto a usual support in such a way that the coated layer contains per sq. m. an amount of silver chloride corresponding to 1.5 g. of silver.

The image-receiving material is prepared by coating a paper support with the following coating composition:

Water cm. 274 Gelatin g 10 Sodium thiosulfate g 12 Sodium sulfide mles 7.7.10 Cobalt nitrate 6 aq. do 7.7.10:-

This suspension is coated in such a way that 13 sq. m. are covered with 1 litre.

After drying, the formed receiving layer is coated with an anti-sticking layer, which facilitates the separation of the light-sensitive emulsion layer from the image-receiving layer.

This anti-sticking layer is coated from a solution of the following composition:

4% aqueous carboxymethyl cellulose 45 Water 155 Sandozol (trade-name for a sulfonated organic oil marketed by Sandoz, Basle, Switzerland) 0.6

The light-sensitive material, in contact with the original to be produced, is exposed and then together with the image-receiving material passed through a developing bath of the following composition:

Water cm. 1000 Sodium sulfite 'g 75 Sodium hydroxide g 10 Potassium bromide g 1 Hydroquinone g 16 l-phenyl-3-pyrazolidone g 1 When leaving the developing bath both layers are squeezed into close contact and then separated from each other after 10-20 sec. A copy of the original with neutral image tone is apparent in the image receiving layer.

Examples 2-4 The same results are obtained by substituting 6-methyltetrahydro-2H-1,3-0xazine-2-thione, 4,4,6-trimethyl tetrahydro-ZH-1,3-thiazine-2-thione and 4,4,6-trimethy1 tetrahydro-ZH-1,3-oxazine-2-thi0ne for fi-methyl-tetrahydro- 2H-1,3-thiazine-2-thione. If no compounds according to the invention are present, copies with a brown image tone are obtained.

Example 5 The light-sensitive material, prepared as described in Example 1 containing, however, no black-toning agent is passed together with the image-receiving material through the following developing composition containing a black-toning agent.

Sodium sulfite g 50 Sodium hydroxide g 6.6 Potassium bromide g 0.3 Hydroquinone g 10.5 l-phenyl-3-pyrazolidone g 0.6 6-methyltetrahydro-2H-l,3-thiazine-2-thione g 0.05 Water up to cm. 1000 The advantage of this bath with regard to a common bath, e.g. with 1-phenyl-5-mercapto-1,2,3,4-tetrazole for improving the image tone, is a more energetic development in a shorter developing time. Moreover, the copy of the original which is apparent in the image-receiving material possesses a more'neutral image tone.

Example 6 The same favourable result is obtained when in Example 5 6-rnethyltetrahydro-2H-1,3-thiazine-2-thione is replaced by a same amount of 4,4,6-trimethyltetrahydro- 2H-l,3-thiazinc-2-thione.

The optimum concentration of both compounds is Example 7 A usual paper support for the silver complex diffusion transfer process is coated with a layer from the following coating composition:

A silver chloride emulsion paper containing per sq. m. an amount of silver chloride which corresponds to 1.5 g. of silver, is exposed in contact with an original to be reproduced and then, together with the image-receiving material, passed through a developing bath of the following composition:

Sodium sulfite g Sodium hydroxide g 10 Potassium bromide g 0.5 Hydroquinone g 16 1-phenyl-3-pyrazolidone g 1 Water, up to .cm.*.. 1500 On leaving the developing bath both layers are squeezed into close contact and then separated from each other after 10-20 sec. A copy of the original with a neutral image tone is apparent in the image-receiving layer,

whereas a material containing-no black-toning agent shows a brown image-tone.

Example 8 Example 7 is repeated replacing, however, the silver sulfide in the image-receiving material by 8 mg. of colloidal silver.

Example 9 Example 7 is repeated replacing, however, the silver sulfide in the image-receiving material by a mixture of 1.2.10 mole of sodium sulfide and 3.1.10* mole of cobalt nitrate 6 aq. The amount of 6-methyltetrahydro- 2H-l,3-thiazine-2-thione is tripled, since heavy metal sulfide nuclei such as cobalt sulfide nuclei are less active black-toning agents than silver sulfide or colloidal silver nuclei which absorb the black-toning agents much better and so make them more effective.

Example 10 A usual paper support'is coated with an image-receiving layer from the following suspension:

Gelatin g 40 Colloidal silver sulfide mole 1.64 10* 4,4,6-trimethyltetrahydro 2H-1,3-oxazine-2-thione in ethanol (0.20% solution) cm. 50 Aqueous formaldehyde (20%) -cm. 2 Water, up to cm. 1000 This suspension is coated in such a way that with 1 litre 10 sq. m. are covered.

After drying, the formed image-receiving layer is coated, with an antisticking layer from the following solution:

Water cm. 370 Sodium thiosulfate 5 aq 25 Aqueous carboxymethyl cellulose (2%) cm. 600

Sandozol (trade name) cm. 5

The solution is coated in such a way that 14 sq. m. are covered with 1 litre.

A silver chloride emulsion an amount of silver chloride silver nitrate, is exposed to an paper, containing per sq. m. corresponding to 1.6 g. of original to be reproduced,

in contact therewith and then together with the above image-receiving material passed through a developing bath of the following composition:

Sodium sulfite g. 75 Sodium hydroxide g 10 Potassium bromide g 1 Hydroquinone g 16 1-phenyl-3-pyrazolidone g 1 Water, up to cm.- 1000 On leaving the developing bath both layers are squeezed into contact and then separated from each other after 20 see. A copy of the original with neutral image-tone is apparent in the image-receiving layer (density: 1.40).

If this example is repeated without using a blacktoning agent a brown image tone is obtained. If the example is repeated substituting a same amount of l-phenyl- S-mercapto-1,2,3,4-tetrazole for the amount of blacktoning agent according to the invention, one copy is obtained having a neutral image tone by a markedly lower density (0.95).

Example 11 An image-receiving material is prepared by coating a usual paper support with the following suspension:

Gelatin g 40 Sodium thiosulfate 5 aq. g 35 Colloidal silver sulfide mole 1.64 Ethanol cm. 100 Aqueous formaldehyde (20%) cm. 5 Sandozol (trade name) cm. 1 Water, up to cm. 1000 This suspension is coated in such a way that 11 sq. m. are covered with 1 litre.

The light-sensitive material from Example 10 is imagewise exposed and while being pressed into contact with the above image-receiving material, passed through the following developing composition:

Sodium sulfite g Sodium hydroxide g 10 Potassium bromide g 1 Hydroquinone g 16 1-phenyl-3-pyrazolidone g 1 4,4,6-trimethyl-tetrahydro-2H-1,3-oxazine-2- thione g 33 Water, up to cm. 1000 Both materials are separated after 20 sec. of contact. An image is obtained with a perfectly neutral image tone, whereas a copy with a brown image tone is obtained when no black-toning agent was added to the bath.

Example 12 Example 11 is repeated substituting in the developing composition a same amount of tetrahydro-ZH-1,3-thiazine- Z-thione for 4,4,6-trimethyl-tetrahydro-ZH-1,3-oxazine-2- thione. Again, a copy with a perfectly neutral image tone is obtained.

Example 13 Example 10 is repeated substituting, however, in the coating suspension for the image-receiving layer mole of colloidal nickel sulfide for l.64 l0 mole of colloidal silver sulfide and 50 cm. of 1% solution of tetrahydro-ZH-1,3-oxazine-2-thione in ethanol for a same amount of 0.2% solution of 4,4,6-trimethyl-tetrahydro- 2H-1,3-oxazine-2-thione in ethanol. Again, a copy with a perfectly neutral image tone is obtained.

We claim:

1. A photographic silver complex diffusion transfer process comprising developing with a developing solution an image-wise exposed light-sensitive silver halide emulsion layer and image-wise diffusion of the non-developed and complexed silver halide from said emulsion layer into a non-light-sensitive image-receiving layer of an imagereceiving material where the complexed silver halide is converted into a silver containing image in the presence of development nuclei and of at least one compound provided in at least one of said developing solution and said image-receiving material having the following general formula or tautomeric structure thereof:

R5-C I R4C NH wherein:

X is an atom selected from the group consisting of a sulfur atom and an oxygen atom, and

each of R R R R R and R is hydrogen or lower alkyl.

2. A developing bath for being used in a silver complex diffusion transfer process and comprising at least one compound having the following general formula or tautomeric structure thereof:

K Rs-C 3=s R47C\ /NH R 0 wherein:

X is an atom selected from the group consisting of a sulfur atom and an oxygen atom, and

each of R R R R R and R is hydrogen or lower alkyl.

3. A photographic image-receiving material for being used in a silver complex diffusion transfer process, the image-receiving layer of which comprising at least one compound having the following general formula or tautomeric structure thereof:

wherein:

X is an atom selected from the group consisting of a sulfur atom and an oxygen atom, and each of R R R R R and R is hydrogen or lower alkyl. 5. The process of claim 1, further characterized in that the compound is tetrahydro-ZH-1,3-thiazine-2-thione.

UNITED STATES PATENTS 2,774,667 12/1956 Land 96--29 2,987,396 6/1961 Williams 96-29 1 0 1/1962 Tregillus 9629 12/ 1964 Willems et a1. 9629 FOREIGN PATENTS 10/ 1958 Belgium. 3/ 1962 Belgium. 7/ 1956 Great Britain. 4/1957 Great Britain. 10/ 1957 Great Britain. 5/ 1961 Great Britain. 7/1962 Great Britain.

OTHER REFERENCES Photographic Science and Engineering, 4, pp. 257-263 NORMAN G. TORCHIN, Primary Examiner. G. H. BJORGE, R. MARTIN, Assistant Examiners. 

1. A PHOTOGRAPHIC SILVER COMPLEX DIFFUSION TRANSFER PROCESS COMPRISING DEVELOPNG WITH A DEVELOPING SOLUTION AN IMAGE-WISE EXPOSED LIGHT-SENSITIVE SILVER HALIDE EMULSION LAYER AND IMAGE-WISE DIFFUSION OF THE NON-DEVELOPED AND COMPLEXED SILVER HALIDE FORM SAID EMULSION LAYER INTO A NON-LIGHT-SENSITIVE IMAGE-RECEIVING LAYER OF AN IMAGERECEIVING MATERIAL WHER THE COMPLEXED SILVER HALIDE IS CONVERTED INTO A SILVER CONTAINING IMAGE IN THE PRESENCE OF DEVELOPMENT NUCLEI AND OF AT LEAST ONE COMPOUND PROVIDED IN AT LEAST ONE OF SAID DEVELOPING SOLUTION AND SAID IMAGE-RECEIVING MATERIAL HAVING THE FOLLOWING GENERAL FORMULA OR TAUTOMERIC STRUCTURE THEREOF: 